Collecting tank, heat exchanger, and method for producing a collecting tank

ABSTRACT

The invention relates to a collecting tank ( 11 ), especially a charge-air tank or a coolant tank, consisting of plastic and comprising at least one tie rod ( 12 ) which is integrated into the collecting tank ( 11 ) or is connected to the same in a fixed manner or in such a way that it forms a single component therewith. Said tie rod ( 12 ) comprises at least one insert ( 13 ).

The invention relates to a collecting tank, in particular a charge-air tank or a coolant tank for a motor vehicle, according to the precharacterizing clause of claim 1, to a heat exchanger according to the precharacterizing clause of claim 11 and to a method for producing a collecting tank.

Conventional, injection-molded plastic charge-air tanks, which are subjected to great loads, to be specific high temperatures and high pressures, are often formed in regions with particularly high loads with tie rods, which form a connection from one wall of the charge-air tank to the other. These tie rods are generally allowed for in the form in which the tank is produced and are injection-molded along with the charge-air tank from the same material. However, such a charge-air tank still leaves something to be desired.

Therefore, EP 0 641 985 B1 discloses a heat exchanger tank with a number of reinforcing struts, which are formed separately from the heat exchanger tank and inserted into depressions, which extend between opposite walls of the heat exchanger tank, after the completion of the heat exchanger tank. In this case, however, production is relatively complex, so that such a heat exchanger tank also still leaves something to be desired.

It is the object of the invention to provide an improved collecting tank and/or heat exchanger.

This object is achieved by a collecting tank with the features of claim 1 and by a heat exchanger with the features of claim 11. Advantageous refinements are the subject of the subclaims.

According to the invention, the tie rod, which is formed in one piece with the collecting tank, preferably from plastic, or is at least connected to it in a fixed manner, in particular by means of being molded in, comprises an insert. This is placed into the mold, in particular before the injection-molding. In principle, it is also possible to push the tie rod into openings made during the injection-molding and subsequently seal it, whereby an integral connection is possible, or fasten it by means of a resilient undercut, such as a latching lug for example, whereby a nonpositive connection can be realized.

The insert is preferably a reinforcing element and/or a cooling element. The latter is appropriate in particular in the case of charge-air tanks exposed to high temperatures, since the material temperatures can in this way be specifically lowered in the regions that are subjected to the greatest loading. In this way, the oxidative aging of the plastic is slowed, whereby the service life increases. Furthermore, less expensive plastics can also be used or, in certain cases, the use of plastics instead of aluminum becomes possible in the first place.

The insert is preferably a metal insert part, a metal strip, a metal tube, an insert part of fibrous material, a tape of fibrous material and/or a fiber, the fibrous material or the fiber being glass or carbon fibers in particular.

An encapsulation with a plastic is preferably provided. This applies in particular to the variant in which the tie rod is pushed in and sealed after the injection-molding. The plastic encapsulation, which consists in particular of a plastics material that allows itself to bond without any problem with the plastics material of the collecting tank, makes a very good, preferably integral, connection of the plastics materials possible.

For cooling by means of a fluid flowing through, the insert is preferaby formed in a hollow manner, in particular with a substantially circular or oval cross section. In this case, it is also possible for a number of thin tubes to be arranged next to one another, formed separately or in one piece.

Furthermore, the insert may consist of a material with good heat conduction, such as copper or aluminum for example. This also applies in particular to the previously mentioned inserts formed in a hollow manner.

The insert preferably protrudes outward beyond the outer side of the collecting tank and/or ends in a projection of the collecting tank, in particular in a rib of the same. If the insert ends in a rib or the like, very good anchorage can take place, since, for thermal reasons, the ribs exposed to the ambient temperature have a high modulus of elasticity even during driving operation.

According to a preferred refinement, a collecting tank according to the invention is used in a heat exchanger, heat exchange tubes opening out into the collecting tank. In particular, the heat exchanger has corrugated ribs to increase the size of a heat-exchanging surface, the corrugated ribs being soldered for example to the heat exchange tubes. Such heat exchangers can be used in particular in motor vehicles.

Moreover, there is the possibility of using the collecting tank according to the invention in any desired heat exchanger on its own or in conjunction with at least one further collecting tank, it being possible for the at least one further collecting tank to be likewise a collecting tank according to the invention or a collecting tank according to the prior art.

The invention is explained in detail below on the basis of several exemplary embodiments with reference in part to the accompanying drawing, in which:

FIG. 1 shows a heat exchanger with two collecting tanks according to a first exemplary embodiment,

FIG. 2 shows a section transversely through one of the collecting tanks from FIG. 1,

FIG. 3 shows a section longitudinally through the collecting tank from FIG. 2,

FIG. 4 shows a section longitudinally through a collecting tank according to a third exemplary embodiment, and

FIG. 5 shows a section longitudinally through a collecting tank according to a fourth exemplary embodiment.

A collecting-tank 1 according to the invention, formed as a coolant tank, of an air-conditioning system of a motor vehicle consists of polyamide reinforced with glass fibers, with a tie rod 2, which comprises an insert of a glass fiber tape. For the production of the coolant tank, a chemical, exothermally acting blowing agent in granular form is added to a polyamide in granular form, mixed with glass fibers to accelerate the crystallization, the blowing agent being encapsulated with polyethylene, and the granules are mixed with one another and fed to an injection-molding machine.

In a screw of the injection-molding machine, a plastication of the granules takes place in a known way to form a polymer melt as a result of heat (240-290° C.) and pressure. This plastic polymer melt is filled into an injection mold, into which reinforcing elements, in the present case glass fibers arranged in the manner of tapes, which are encapsulated with polyamide, are automatically placed at the locations at which tie rods 2 are intended. In this case, the reinforcing elements are preheated. On account of high temperatures, the blowing agent reacts by emitting thermal energy with the formation of CO₂. The blowing agent or the CO₂ produced brings about faster filling of the injection mold, since a slight shrinkage in the volume of the polymer melt occurs during cooling, so that no plasticated polymer melt, or only a minimal amount, has to be pushed in afterwards to compensate for the shrinkage in volume. The injected polyamide integrally bonds with the polyamide of the glass fiber encapsulation, so as to form tie rods 2 that are integrated in one piece in the coolant tank and reinforced with glass fibers to meet the requirements.

The polymer melt remains in the injection mold until the mold is filled and a certain crystallization and relaxation have taken place. Subsequently, the injection mold is opened, the coolant tank is removed and a clamping frame is immediately inserted to prevent sinking of the coolant tank. According to the method as provided by the invention, the coolant tank has a surface temperature of about 120° C. when it is removed. In this case, the clamping frame may be cooled.

For further processing, a rubber cord seal is placed around an aluminum tank base, the clamping frame is removed from the coolant tank, the coolant tank is placed as quickly as possible, i.e. within about 30-60 seconds, onto the aluminum tank base with the rubber cord seal and pressed in a press.

According to a second exemplary embodiment, not represented in the figure, thin metal tubes, which are intended for reinforcing and cooling the tie rods, are placed into the injection mold and molded in as inserts for a charge-air tank, the ends of the metal tubes protruding from the mold, so that connection to a coolant circuit is possible later. The coolant cooler is generally arranged near the charge-air tank and therefore only minor changes are required for a charge-air tank that is cooled in a certain region, that is to say in the region of the tie rods.

FIG. 4 shows a collecting tank 11, in the present case a charge-air tank, with a tie rod 12, which is reinforced by a molded-in tape of aramid fibers as an insert 13, i.e. the encapsulation of the tape consists of the same material as the collecting tank 11. For production, the tape is conveyed through the injection mold fully automatically and sheared off before demolding.

Shown in FIG. 5 is the use of a perforated geometry as an insert 23, in the present case a specially shaped plate of metal, which is completely encapsulated by the material of the collecting tank 21, as tie rod 22. Apart from metals, other higher-strength materials also come into consideration as materials. For the pre-fixing of the perforated geometry in the injection mold, said geometry may have elevations, which permit easy clamping in the injection mold. 

1. A collecting tank, in particular a charge-air tank or a coolant tank made of plastic, with at least one tie rod, which is integrated into the charge-air tank or coolant tank, formed in one piece with it or connected to it in a fixed manner, characterized in that the tie rod comprises at least one insert.
 2. The collecting tank as claimed in claim 1, wherein the insert is a reinforcing element and/or a cooling element.
 3. The collecting tank as claimed in claim 1, wherein the insert is a metal insert part, a metal strip, a metal tube, an insert part of fibrous material, a tape of fibrous material and/or a fiber.
 4. The collecting tank as claimed in claim 3, wherein the fibrous materials comprise carbon and/or glass fibers.
 5. The collecting tank as claimed in claim 1, wherein an encapsulation of the insert with a plastic is provided.
 6. The collecting tank as claimed in claim 5, wherein the encapsulating material is the same plastic as that of the remaining collecting tank.
 7. The collecting tank as claimed in claim 1, wherein the insert is formed in a hollow manner.
 8. The collecting tank as claimed in claim 7, wherein the insert is formed such that it can be flowed through by a fluid.
 9. The collecting tank as claimed in claim 1, wherein the insert consists of a material with good heat conduction.
 10. The collecting tank as claimed in claim 1, wherein the insert protrudes outward beyond the outer side of the collecting tank and/or ends in a projection of the collecting tank.
 11. A heat exchanger, in particular a charge-air cooler or a coolant cooler, in particular for a motor vehicle, with heat exchange tubes which open out into at least one collecting tank, wherein at least one collecting tank is formed as claimed in.
 12. A method for producing a collecting tank as claimed in claim 1, wherein the insert is directly molded in during the production of the collecting tank and/or is subsequently inserted and sealed into it with an integral bond. 